Painted into a skimpy Hervé Léger minidress, Britney Spears turned plenty of heads at the Wango Tango concert in L.A. on May 14. The star has had her ups and downs with weight (as well as with her personal life), but that night, Britney was tanned and taut, boasting a bod as hot as she had a decade ago, in her …Baby One More Time prime.

As she prepares to launch her Femme Fatale summer tour, the pop princess is back! “Britney’s dropped 20 pounds since her heaviest,” a pal tells OK!.

“The best thing she ever did was cut out alcohol,” the insider says. “It was bloating her, upsetting her blood sugar and causing her cravings.” Indeed, in the past, the 9-year old singer indulged in pizza, cookie-dough ice cream and greasy tacos.

Pals say that steady stream of bad-for-you-food triggered mood swings. “It stressed her out and added to her weight gain,” a source says. “It was a vicious cycle. Now, she seems to finally have control.” So much so that Brit can indulge in a weekly cheat — like enjoying her fave warm ham-and-cheese croissant for breakfast before a rehearsal.

As for the other half of the weight-loss equation — fitness — Britney dances daily to prep for her tour (always her favorite way to burn calories), in addition to training with Jason in her private gym. “Cross-training — mixing cardio, like the treadmill, with weights — is Britney’s strategy when she’s feeling heavy,” a source tells OK!. “And she’s been doing a lot more Pilates lately.”

FOR MORE ON BRIT’S DIET SECRETS, PICK UP THIS WEEK’S ISSUE OF OK! – ON SALE EVERYWHERE TOMORROW!